Power-driven hammer



' G. C- ROBINSON.

Feb. 15, 1949.

POWER DRiIZVEN HAMMER 2 Sheets-Sheet 1 Filed June 4, 1947 IN VEN TOR. C /M B Feb. 15, 1949. G. c. ROUBINSON 2,461,571

POWER DRIVEN HAMMER Filed June 4, 1947 I 2 Sheets-Sheet 2 I uvwszvrozz.

Patented Feb. 15, 1949 UNITED STATES PATENT OFFICE POWER-DRIVEN HAMMER Girard C. Robinson, Maywood, 111.

Application June 4, 1947, Serial No. 752,507

7 Claims. (Cl. 125-33) This invention relates to improvements in power driven hammers.

In my pending application, Serial No. 739,916, filed April 7, 1947, there is disclosed a power driven rotary tool which is so constructed as to make it practical for a relatively small electric motor to drive a tightener for nuts, bolts and the like. In this construction, springs are utilized in which energy is stored when resistance is encountered, and there is means whereby this energy is utilized to deliver a driving force when the nut is nearly set.

It is a general object of the present invention to make use of some of the principles of the construction shown in the aforementioned pending application for the purpose of producing forcible blows on a reciprocating hammer rather than for the purpose of transmitting a rotary motion to the tool. This type of construction is particularly useful in connection with the setting of rivets. It may also be employed for the breaking of pavement, for star drilling, for tie tamping, and for chipping and chiselling. The present invention makes it practical to produce a portable tool of the hammer type having a self-contained electric driving motor.

The present invention is an improvement over the construction shown and described in my pending application entitled Power driven hammer, Serial No. 596,768, filed May 30, 1945 which is now abandoned. In this pending application several expansion springs which normally extend substantially longitudinally of the driving ppindle, are utilized, the springs being subjected to an elongating and twisting force during use. This twisting action has a tendency to fatigue the ends of the springs and cause them to break after a period of use. Furthermore, with this type of construction, if a spring does break, use of the tool cannot be continued until the spring is replaced.

It is a general object of the present invention to improve upon the construction of said prior application by providing a power driven hammer wherein the life of the springs is substantially prolonged and wherein even if a spring should break, use of the hammer can be continued until it is convenient to make a replacement.

A further object of the invention is to provide a power driven hammer wherein the springs can be preloaded to thereby increase the force of the blow in accordance with predetermined requirements. This preloading is accomplished in a simple manner by merely rotating a ring a short distance and setting the ring in a selected position.

It is a general subject of the present invention to improve upon the construction of said prior application by providing a power driven hammer wherein the life of the springs is substantially prolonged and wherein even if a spring should break, use of the hammer can be continued until it is convenient to make a replacement.

A further object of the invention is to provide a power driven hammer wherein the springs can be preloaded to thereby increase the force of the blow in accordance with predetermined requirements. This preloading is accomplished in a simple manner by merely rotating a ring a short distance and setting the ring in a selected position.

A further object of the invention is to provide a power driven hammer wherein there are a plurality of springs arranged and supported in a novel manner for storing energy, said springs being under compression at all times and working in conjunction with each other to provide continuous power for the impact blow of the hammer.

A further object of the invention is to provide a power driven hammer which is easier to manufacture and assemble than prior constructions.

With the above and other objects in view, the invention consists of the improved power driven hammer, and all its parts and combinations, as set forth in the claims, and all equivalents thereof.

In the accompanying drawings, illustrating one complete embodiment of the preferred form of the invention, in which the same reference numerals designate the same parts in all of the views:

Fig. 1 is a longitudinal sectional view through the hammer, part of the inner end of the striking pin or hammer member proper being broken away;

Fig. 2 is a sectional view taken on the line 22 of Fig. 1 but with the impact member and associated rings in a different position of rotation;

Fig. 3 is a fragmentary sectional view taken along the same line as the corresponding por-- tion of Fig. 2 and illustrating the position of the parts at the time of impact;

Fig. 4 is a similar view showing the position of the parts just after impact;

Fig. 5 is a similar view illustrating the position of the parts at approximately the time of withdrawal of the impact jaw from the reciprocatory hammer member:

Fig. 6 is an end view of the impact member alone, part being broken away and shown in section;

Fig. 7 is a view of the spring holding ring looking at the opposite end from that illustrated in Figs. 3, 4 and and Fig. 8 is an end view of the adjustment ring.

Referring more particularly to the drawings, the numeral l0 designates a suitable casing having an operator's handle ll. .Within the casing and spaced from the adjacent wall 9 is an internal wall ll having bearing openings [2 and I3 for receiving ball bearing sets I4 and II. Extending transversely of the internal wall II is a partition I which divides the easing into two main chambers I1 and i3.

Suitably mounted within the chamber I1 is the rotor l9 of an electric motor. One end of the. drive shaft of the motor may be suitably journalled in a ball bearing set 2i. The other end of the drive shaft of the motor is journalled throughthe ball bearing set l4 and has its outer end in the form of a pinion, as at 22. The latter end drives an idler gear 23 which in turn drives a gear mounted rigidly on the end of the driving spindle 25 for the impact member. The driving spindle" is journalled in the ball bearing set I! and in an oppositely positioned ball hearing set 23.,- v

Intermediate the ball bearing sets I! and 28 and within the housing chamber II, the driving spindle 25 is formed with an elongated eccentric part 21. At one end of the eccentric portion 21 is an integral annular shoulder 23 and between said shoulder'and the ball bearing set I! is a concentric spindle portion 29 which is of larger diameter than the portion which is joumalled in the bearing'set l9. Keyed to the spindle portion 29 is an eccentrically formed counterbalance 30.

Mounted loosely on the eccentric portion 21 of the spindle is an impact member 31 provided with a radially projecting impact jaw 32. The engaging portion of the jaw may be faced with a disc of hard, wear-resisting material 33. Projecting toward the right (referring to Fig. 1) from anend face of the impact member is a lug 34. The opposite end-face of the impact member may be countersunk, as at 35, to rotatably receive the circular shoulder 23 at the end of the eccentric portion 21 of the driving spindle.

' Positioned adjacent that end face of the impact member 3| which has the ing 34, is a ring 39. One end face of this ring is formed with a circular' 'spring retaining groove 31 and the other end face is provided with a similar groove 33. v The end face of the ring 36, which is adjacent the impact member 31, is shown in Fig. 7, and it isto be noted that there is a lug 39 fixed within the groove31. The lug 39 is adapted to engage one 'endof a coil spring 49. The coil spring 49 is of a length as to be able to extend entirely around within the groove 31. However, its opposite end (which end is broken off in Fig. 7) is engageable with the lug 34'of the impact member 3i so that the spring 49 may be in various stages of compression depending upon the relative positions of. the lugs 39 and 34.

In the groove 39 in the opposite end face of the ring 33 is' 'a like coil spring 4i, as is clear from Figs; 3, 4 and 5. One end of this spring is engageable with a lug 42 permanently anchored withinl thegroove, and the other end is engageable with-a. lug 43 which projects into the groove from theend face of an adjustment ring 44.

The adjustment ring 44 has set screws 45 In addition, the opposite end face ofthe ring 44 may be formed with dial markings 49, as is illustrated in Fig. 8. I

It is, of course, possible to utilize more than one spring retaining ring 39 end for end. In this way, more springs may be employed and a blow of greater power may be generated. However, for most purposes, the single ring with spring grooves on both ends is satisfactory. It is also possible to utilize a. series of rings having spring grooves in one face only, as is illustrated in my co-pending application, Serial No. 739,916, filed April 7, 1947.

Positioned in an opening 41 of the housing Ill. preferably at the bottom thereof, is a sleeve 43 which slidably receives the shank portion 49 of a reciprocatory hammer member 90. The hammer member has an enlarged head portion to provide an annular shoulder 5| which limits the inward movement. When the shoulder is in the position of Figs. 1 and 2, the inner end of the shank 49 is in a position to receive an impact from the jaw 32. The .hammer member may have its outer end recessed, as at 52, for rivet setting purposes. Any other reciprocatory tool may be substituted for the hammer member illustrated. For example, tools for breaking pavements, for tamping ties, for chipping, for chiselling, or for star drilling, may be efliciently operated by the present device.

In use of the device, when the electric motor is started, engagement of the pinion 22 with the gear 23 and engagement of the latter with the gear 24 will cause driving of the driven spindle 29 and rotation of the eccentric portion 21 in the direction indicated by the arrows in Figs. 3, 4 and 5 Rotation of-the eccentric portion 21 will cause corresponding rotation of the adjustment ring 44 which is locked thereto. This rotating movement will be transmitted from the lug 43 of the adjustment ring through the spring 4| and the .lug 42 to the ring 38. On the other side of the ring rotation will be transmitted from the lug 39 to the spring 49 and from the latter, to the lug 34 of the impact member 3|.

With this train of driving forces, then assuming that the parts are in the position of Fig. 3, just after an impact blow has been delivered, continued rotation of the driving spindle will cause the lug 43 of the adjustment ring to compress the spring andstore up energy, as is indicated in Figs. 4 and 5. On the other side of the ring the lug 39 will compress the spring between it and the lug 34 of the impact member storing up additional energy. During such movement the wide portion A of the eccentric moves to the position of Fig. 5 to cause the jaw 32 to be drawn radially inwardly along the top of the shank 49 of the reciprocatory hammer. While this is occurring, however, considerable energy will be stored up in the springs. Upon continued rotation and approximately at the position of Fig. 5, the jaw 32 will ultimately be pulled a suiiicient distance radially inwardly to entirely clear the top of the shank 49. The energy stored in the compressed springs will then forciby throw the jaw 360 into re-engagement with the shank of the rec procatory hammer. Durin the abovedescribed operation the weight of the jaw augmented by the weight of the impact member 3!. and together with the energy of the springs will deliver strong blows to the hammer member.

These impact blows will be continued as long as the motor is in operation.

8 Energy may be prestored in the springs II and ll of the ring II by making a proper adjustment of the adjustment ring 44. Referring to Fig. 8, by loosenin the set screws I and rotating the ring 44 counterclockwise to a predetermined position on the dial 4', the springs may be preloaded a predetermined amount to give a greater impact blow. By turning the adjustment disc in the opposite direction it is possible to lighten the impact blow where this is desirable.

It is apparent that the construction is simple to manufacture and assemble. and that any number of spring retaining rings 30 may be employed depending upon requirements. Because 01' the use 01' a plurality of springs, even it one oi the springs should break, the tool can still be used, with somewhat lessened efllciency, until it becomes convenient to make a replacement. If desired, instead of having a single sprin in each of the grooves, as is shown in Fig. 3, the springs 40 and I may each be formed of multiple sections.

Various changes and modifications may be made without departing from the spirit of the invention, and all of such changes are contemplated as may come within the scope of the claims.

What I claim is:

1. In a power driven implement, a tool holder, a reciprocatory tool slidably mounted in said holder, a rotatable impact member having a circular opening therein and having a part positioned for impact engagement with said tool which is releasable by radial movement of said part out of engagement with said tool, means includin a driving spindle having an eccentric rotatable within said circular opening of said impact member for eflecting said radial movement after impact, a compression spring extending circumferentially around at least a portion of said eccentric, means on said spindle engageable with one end of said spring to transmit a driving force thereto in a circumferential direction when the spindle is rotated, means for transmitting said driving force from the other end of said spring to said rotatable impact member, said spring being positioned to be compressed aiter impact and to cause automatic forcible re-engagement with said tool after release, and a counterweight on said spindle projecting in a direction opposite from the direction which said impact part projects.

2. In a power driven implement, a tool holder, a reciprocatory tool slidably mounted in said holder, a rotatable impact member having a circular opening therein and having a part positioned for impact engagement with said tool which is releasable by radial movement of said part out of engagement with said tool, means including a driving spindle having an eccentric rotatable within said circular opening of said impact member for effecting said radial movement after impact, a compression spring extending circumferentially around at least a portion of said eccentric, a retaining rin for said spring within which said eccentric is rotatable, means on said spindle engageable with one end of said spring to transmit a driving force thereto when the spindle is rotated, and means for transmitting said driving force from the other end of said spring to said rotatabl e impact member, said spring being positioned to be compressed in said retaining ring after impact and to cause automatic forcible reengagement with said tool after release.

3. In a power driven implement, a tool holder, a

reciprocatory tool slidably mounted in said holder, a rotatable impact member having a circular opening therein and having apart positioned for impact engagement with said tool which is releasable by radial movement of said part out 01 engagement with said tool, means including a driving spindle having an eccentric rotatable within said circular opening of said impact member for efl'ecting said radial movement after impact, a compression spring extending circumferentially around at least a portion of said eccentric. a retaining ring for said spring within which said eccentric is rotatable. means on said spindle engageable with one end 01- said spring to transmit a driving force thereto when the spindle is rotated and means including the retaining ring for transmitting said driving force from the other end of said spring to said rotatable impact member, said spring being positioned to be compressed in said retaining ring after impact and to cause automatic forcible re-engagement with said tool after release.

4. In a power driven implement, a tool holder, a reciprocatory tool slidably mounted in said holder, a rotatable impact member having a circular opening therein and having a part positioned for impact engagement with said tool which is releasable by radial movement of said part out oi! engagement with said tool, means including a driving spindle having an eccentric rotatable within said circular opening oi! said impact member for effecting said radial movement after impact, a compression spring extending in a circumferential direction around said eccentric, a retaining ring within which said eccentric is rotatable and having a circular groove within which said spring is positioned, means on said spindle engageable with one end of said spring to transmit a driving force thereto when the spindle is rotated, and means for transmitting said driving force from the other end of said spring to said rotatable impact member, said spring being so supported as to be compressed in the groove of said holding ring after impact and to cause automatic re-engagement of said impact member with said tool after release.

5. In a power driven implement, a tool holder, a reciprocatory tool slidably mounted in said holder, a rotatable impact member having a circular opening therein and having a part positioned for impact engagement with said tool which is releasable by radial movement of said part out of engagement with said tool, mean including a driving spindle having an eccentric rotatable within said circular opening of said impact member for effecting said radial movement after impact, a retaining ring within which said eccentric is rotatable and having a circular groove, a lug in said groove, a compression spring in said groove having an end engaging said lug, and means driven by said spindle and engageable with the opposite end of said spring to transmit a driving force thereto when the spindle is rotated, there being a connection between said retaining ring and rotatable impact member for transmitting said driving force from said ring to said impact member, said spring being compressible against said lug after impact and bein adapted to cause automatic forcible re-engagement of the impact member with said tool after release.

6. In a power driven implement, a tool holder, 2. reciprocatory tool slidably mounted in said holder, a rotatable impact member having a circular opening therein and having a part positioned for impact engagement with said tool 7 which is releasable by radial movement of said part out of engagement with said tool, means including a driving spindle having an eccentric rotatable within said circular opening of said impact member for effecting said radial movement ai'ter impact, a retaining ring within which said eccentric is rotatable and having a circular groove, a lug in said groove, a compression spring in said groove having an end engaging said lug. means driven by said eccentric and engageable with the opposite end of said spring to transmit a driving force thereto when the eccentric is rotated, there being a connection between said retaining. ring and rotatable impact member-tor transmitting said driving force to the latter, said spring being compressed against said lug after impact and causing automatic re-engagement of said impact member with said tool after release, said eccentric driven means including an adjustment ring through which said eccentric extends and said adjustment ring being provided with a releasable setting member for connecting said ring in a predetermined position of rotation on said eccentric.

7. In a power driven implement, a tool holder. a reciprocatory tool slidably mounted in said holder, a rotatable impact member having a circular opening therein and having a part positioned for impact engagement with said tool which is releasable by radial movement of said part out of engagement with said tool, means including a driving spindle having an eccentric rotatable within said circular opening of said impact member for eflecting said radial movement after impact, a retaining ring within which said eccentric is rotatable and having a circular groove in each end face, a lug in each groove, a compression spring in each groove having an endengaging the lug therein and having ai'ree end, means driven by said eccentric and engageable with said free end of the spring in one of said grooves to transmit a driving force thereto when the eccentric is rotated, a mg on the rotatable impact member projecting into the other groove end engageable with the free end 0! the spring therein for transmitting a driving force from said spring'to said impact member, said springs being compressible after an impact and being adapted to cause automatic re-engagement 01' said impact member with said tool after release. g 1 GIRARD v( L ROBINSOIL REFERENCES crran UNITED STATES PATENTS I Name 7 Date Larocca Aug. 31, 1926 FOREIGN PATENTS Country Date France Oct. 6, 1941 Number Number 

